I made a list of drugs for pain relief as that was what was asked for. There are very few situations (arguably none) in which all drugs are practical.

Expecting any drug to replace opioid is very unrealistic at this time and as I have commented on, dealing with chronic pains should be multidisciplinary and not entirely reliant on just pharmaceutical therapy for the most effective way of tackling the issue.

One of the largest barriers is tackling patient (and indeed many healthcare provider) mindsets and psychologies. Opioid rotation is not a long term solution. Opioid reduction is the main aim but requires a huge turnaround of thinking/effort/money.

Prevention is better than cure generally. Stopping the opioid problem in a patient beforenit deveoops into a massive chronic issue is far better than trying to sort it when they aren on 160mg BD and it's five years down the line. One situation that can be worked on is the acute pain apatient who comes to hospital (e.g. After a trauma). If the analgesia is effectively tackled then, with the likes of the medications I have mentioned, and they get discharged without the need for ever escalating opioid prescriptions, how is that a bad thing? If you disagree and you think they should just get ever escalating doses of single agents then, again, that's your opinion.

As of yet there is no panacea and I doubt there ever will be. Based on your name I'm guessing that you are somehow involved in the pharmaceutical industry? If this is the case then no doubt you are aware of how difficult it is to create a drug that has decent efficacy, acceptable tolerance and safety profile and a cost efficient process of manufacturing, distribution and marketing.

I never said

Ketamine is very variable in terms of side effects depending on the doses you use. I doubt it would be good for long term use but acutely it is awesome because it remains cardiovascular stable so it's great for trauma patients who have lost loads of blood, it's a bronchodilator so it's great for asthmatics and you don't have as much respiratory/airway loss like other anaesthetic induction agents. But that is all from a general anaesthetic dosing point of view.

At lower doses I've used it for dressing changes on burns patients and for manipulating kids dislocated limbs. You give a small dose, wait for them to go into a sort of fugue state and then pop the shoulder back in.

It is associated with the potential for profound hallucinations and increased salivation though. It provides a dissociated consciousness. One patient described it as like he was watching what we were doing to him as if it was like watching a TV show. No pain at all but it didn't feel real. Some hate that feeling, some don't care.

Again though I suspect long term use, which I am not familiar with,comes with side effects and problems.

Nerve blocks can last between a few hours and a full day. Depends on what you use, where it is used and how much. But it's labour intensive. Not really something that can be done every day. Plus there is alway the risk that the needle causes damage to the nerve if the person isn't careful with it.

A few places for chronic pain give IV lidocaine infusions. You come in for a few hours, get the infusion with monitoring. Then go home the next day. Again labour intensive and so often the funding isn't available to have it in many locations.

The best therapies in terms of long term benefits are usually physiotherapy and psychology. Ultimately if a pain becomes a chronic pain, the neural pathways alter and essentially don't work how they should do. Therefore removing the pain entirely often becomes impossible and those two therapies help the most because they help the patients accept and deal with the pain so they can get on with life. Unfortunately many patients are unwilling to accept this reality and believe there is a magic cure, a silver bullet, a perfect pill that sorts everything out.